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Grounding in mixed synthesizer circuit - RF Cafe Forums
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Guest
Post subject: Grounding in mixed synthesizer circuit
Unread
postPosted: Wed Apr 06, 2005 8:02 am
Hello everyone!
I want
to design a frequency synthesizer circuit; but I don't know how design
analog and digital grounds. Should these two grounds be connected together
or isolated from each other?
Thanks for help and time.
mohammad
Top
Itay
Post subject:
Unread postPosted:
Wed Apr 06, 2005 8:21 am
Hi mohamad,
The analog and digital
voltages should be provided from different regulators, each will have
its own ground. Then you should connect both grounds by a wide trace
near the regulators.
This will provide good isolation between
the voltages, and eliminate ground loops and noise usually associated
with such designs.
Another advice for synthesizer is to use a
"super filter" circuit for the VCO supply. This circuit is based on
NPN transistor with bypass capacitors at both base and collector (use
a tantalum capacitor at the base) that is used to filter the supply
voltage of the VCO. This circuit reduces the supply voltage from the
regulator to the level required by the VCO. Make sure that the transistor
is in the active region of operation. Use a voltage divider at the base.
This circuit will enhance your phase noise performance.
Hope
this helps,
Itay
Top
Guest
Post subject:
Unread postPosted: Thu Apr 07, 2005 1:40 am
In The Name of God
Dear Itay.
Thanks for your help and time. Some companies produce
integrated microwave frequency synthesizers that include VCO. Should
the RF and digital grounds for these products be isolated too?
Thanks
if you give me your email address.
Also I want to have PDF of some
of microwave books. Can you help me?
Thanks.
With best regards,
Mohammad
Itay wrote:
Hi mohamad,
The analog and digital
voltages should be provided from different regulators, each will have
its own ground. Then you should connect both grounds by a wide trace
near the regulators.
This will provide good isolation between
the voltages, and eliminate ground loops and noise usually associated
with such designs.
Another advice for synthesizer is to use a
"super filter" circuit for the VCO supply. This circuit is based on
NPN transistor with bypass capacitors at both base and collector (use
a tantalum capacitor at the base) that is used to filter the supply
voltage of the VCO. This circuit reduces the supply voltage from the
regulator to the level required by the VCO. Make sure that the transistor
is in the active region of operation. Use a voltage divider at the base.
This circuit will enhance your phase noise performance.
Hope
this helps,
Itay
Top
Guest
Post subject:
Unread postPosted: Thu Apr 07, 2005 3:26 am
Hi Mohammad,
Yes the grounds should be connected as I mentioned in this type
of synthesizers too. I have used this kind of synthesizers as well (ADF4360
series of Analog Devices)
My email address is: itre27@012.net.il
Thanks,
Itay
Posted 11/12/2012
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